Amniotic fluid embolism (AFE) is defined as a disease accompanied by pathological conditions of a pulmonary hypertension caused by obstruction of pulmonary capillary and of a cardiorespiratory failure therefrom, which are induced by inflow of amniotic fluid into maternal blood. Recently, not only an embolism by amniotic fluid but also an anaphylactoid reaction by amniotic fluid components has been indicated as a cause of AFE. Incidence of AFE is rare, but when once it occurs, it leads to a life-threatening status, such as maternal death, in a short time (see, Non-patent document 1, 2).
AFE is classified to two categories; one is established AFE which is confirmed by a histopathological examination after autopsy, and another one is potential AFE which meets three of the following diagnostic criteria for AFE:
Diagnostic criteria for potential AFE:
(1) Developed during pregnancy or within 12 hours after delivery;
(2) Intensive medical treatment to one or more of the symptoms or diseases below:
                (a) cardiac arrest,        (b) massive bleeding of unknown cause within 2 hours after delivery,        (c) disseminated intravascular coagulation (DIC),        (d) respiratory failure,(3) Observed findings and symptom cannot be explained by the other diseases (see, Non-patent document 1).        
Further, serological method can be also employed as a supplementary diagnosis for AFE. The method aims to detect a specific substance derived from amniotic fluid or meconium in maternal blood. Zinc coproporphirin 1 (Zn-CP1) and sialyl Tn (STN) can be used for the purpose (see, Non-patent document 1).
For treatment of AFE, anti-shock therapy (such as, airway opening, blood vessel securing, fluid replacement, administration of anti-shock agent) and anti-DIC therapy (such as, administrations of antithrombin and/or fresh frozen plasma (FFP)) have been basically employed. However, as the mortality rate is still high, further effective therapeutic method for AFE has been strongly desired in addition to these conventional therapeutic methods.
On the other hand, regarding involvement of complement system in pathophysiology of AFE, it has been reported that complements C3 and C4 are decreased in maternal blood of patients with DIC, but no report has been made on the involvement of C1-inhibitor in AFE.
Therefore, there has been no description or suggestion on the use of C1-inhibitor for the treatment of AFE.